The present invention relates to an air-conditioning system that provides an engine driving a vehicle and a compressor driven by a motor due to electric power supplied from a battery.
Japanese Unexamined Patent Publication No. 2000-142091 discloses an air-conditioning system that has an engine, a crankshaft, a link gear, a starter motor for starting the engine, a pinion gear, a solenoid, an electromagnetic clutch, a controller for controlling the electromagnetic clutch and a compressor. The pinion gear is secured to an output shaft of the starter motor so as to move back and forth, and engages with the link gear linking with the crankshaft of the engine by energizing the solenoid upon starting the engine. As the starter motor rotates, the engine starts through the engaged gears. The output shaft of the starter motor is coupled to the compressor through the electromagnetic clutch, which is controlled for connecting and disconnecting due to an electric current supplied from the controller. The electromagnetic clutch is disconnected upon starting the engine, so that the starter motor is only used for starting the engine. Therefore, a load on the starter motor upon starting the engine is decreased. Meanwhile, while the starter motor and the engine are disconnected from each other, the starter motor drives the compressor after the electromagnetic clutch is connected. Therefore, the air-conditioning is ensured during a stop of the engine.
However, according to the above-mentioned structure, two coupling mechanisms are provided for decreasing the load, which acts on the starter motor while the air-conditioning system is operating during the stop of the engine, or which acts on the starter motor upon starting the engine. That is, one of the mechanisms is provided for connecting and disconnecting a power transmitting path between the starter motor and the engine, and the other is the electromagnetic clutch for connecting and disconnecting another power transmitting path between the starter motor and the compressor. Accordingly, such structure causes the system to become large and complicated.
The present invention addresses the above-mentioned problems traceable to two coupling mechanisms by simplifying the structure of the air-conditioning system.
According to the present invention, an air-conditioning system for a vehicle including a refrigerant circuit and an engine, has a compressor in the refrigerant circuit, a battery, an electric motor and a mechanism operative to controllably connect and disconnect a power transmitting path between the engine and the motor. The motor is connected to drive the compressor when energized by the battery. A first controller is operative to control the electric power supplied to the motor from the battery. A capacity control mechanism is responsive to the controller to maintain the discharge capacity of the compressor below a predetermined value upon starting the engine by the motor.
Accordingly, the discharge capacity of the compressor attains a value below the predetermined value upon starting the engine by the motor. Therefore, a load on the motor for driving the compressor attains a value below the predetermined value upon starting the engine by the motor. Thereby, without a coupling mechanism operative to controllably connect and disconnect another power transmitting path between the motor and the compressor, such as an electromagnetic clutch, the load on the motor is decreased upon starting the engine. Also, the maximum load on the motor may easily be decreased. As the load on the motor decreases, lifetime of the battery may lengthen. The motor may not undesirably stop due to shortage of the electric power supplied from the battery during a stop of the engine, such as an idle stop.
According to the present invention, a method for controlling an air-conditioning system for a vehicle including a refrigerant circuit and an engine, includes receiving a signal for starting the engine, maintaining the discharge capacity of a compressor in the refrigerant circuit below a predetermined value, supplying an electric motor operatively connected to the compressor with electric power, and starting the engine by the motor.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.